使用ASP.NET 3.5的每个用户操作上的“请等待”图像

In our ASP.NET 3.5 application, we would like to implement a "Please wait.." feature : on every user action (button click, tab change, etc.) we would display a little spinner on top of the page (actually in a separate frame that we use already have).In our ASP.NET 3.5 application, we would like t